They managed this reasonably well when testing the so-called Wilma method. Basically those with window seats board first, then those with seats in the middle and lastly, those with seats by the aisle. But the best method was the Steffen method, named after the astrophysicist Jason Steffen. After many computer simulations he came to the flowing conclusion; fill every other window seat on one side, then every other window seat on the other side, after that fill the rest of the window seats in the same order, then the same procedure with the middle seats and then the ones by the aisle.
The Steffen method showed up as twice as efficient as the block method, according to an article in SvD. But it does demand a lot from both the staff and the passengers at the gate.
For those of us who swear under our breath about the chaos when boarding, it would have helped a lot if everyone only had ONE piece of hand luggage and removed their outer garments before boarding.